Challenges in differential diagnosis between obstructive and non‐obstructive azoospermia

Abstract

Background: Some cases of non‐obstructive azoospermia (NOA) are characterized by normal clinical parameters, including testicular volume and levels of reproductive hormones, mimicking obstructive azoospermia (OA).

Methods: We performed a retrospective review of a consecutive series of 1417 patients undergoing primary surgical sperm retrieval between 2014 and 2023. Follicle‐stimulating hormone (FSH) level below 7.6 IU/l and normal testicular size with a long axis measurement >4.6 cm were used as criteria to suspect OA.

Results: Four hundred and eighteen patients with normal testicular volume and FSH levels had an initial diagnosis of OA. Among them, 243 (58.1%) had histological signs of spermatogenic dysfunction, and 175 (41.9%) had true OA. One hundred eleven patients had long‐standing obstruction (median: 16.5 years) with a median Bergmann–Kliesch score (BKS) of 5 (interquartile range [IQR]: 4–6) and 100% sperm retrieval rate (SRR), though some required microdissection testicular sperm extraction (microTESE). Fifty‐eight patients with a history of epididymo‐orchitis had a median BKS of 4 (IQR: 2–6) and 100% SRR. Twenty patients with a history of unjustified medical treatment for male infertility had a median BKS of 3 (IQR: 1–4) and 80% SRR. Fifty‐four patients had uniform maturation arrest with a 5.5% SRR on microTESE.

Conclusion: Men with normal testicular volume and FSH level may have evidence of spermatogenic failure on pathology. Patients with complicated seminal tract obstruction commonly have hypospermatogenesis, but true NOA caused by uniform maturation arrest may also be observed. Patient counseling for suspected OA should not be overly optimistic, and couples should be warned about possibility of conversion to microTESE and risks of negative sperm retrieval.

Keywords

azoospermia / male infertility / sperm retrieval

1 INTRODUCTION

Use of advanced assisted reproduction technology (ART) has significantly improved pregnancy rates in infertile couples with azoospermia in male partners. It is still important to distinguish between obstructive azoospermia (OA) and non‐obstructive azoospermia (NOA), however, as these two conditions are significantly different. OA is a rather benign condition with excellent reproductive outcomes, which is sometimes curable with surgical reconstruction[1–4]. NOA, on the other hand, is difficult to treat and requires microdissection testicular sperm extraction (microTESE) in most cases. Surgically retrieved sperm in NOA are then used for intracytoplasmic injection procedure with relatively modest outcomes[5,6]. Therefore, distinction between OA and NOA is essential for patient counseling to provide adequate expectations.

The overall incidence of azoospermia is thought to be around 1%–2%, though the exact numbers were not updated for several decades[7,8]. NOA is more common than OA. About 40% of azoospermia cases may be attributed to obstruction, though these numbers may vary in different populations[9]. Its etiology may remain unknown despite extensive diagnostic search. On the contrary, OA has distinct etiology in most cases, being congenital or acquired[10]. Imaging studies may reveal the exact site of obstruction, which may influence further clinical decision‐making[11].

Differential diagnosis between OA and NOA is possible by evaluating patient's history, physical examination findings, semen analysis, endocrine parameters and genetic screening results[12–14]. It was shown that 96% of patients with OA have follicle‐stimulating hormone (FSH) levels below 7.6 IU/l and normal testicular volume (a long axis measurement > 4.6 cm), while 89% of patients with NOA have elevated FSH and decreased testicular volume[15]. This rule is commonly used in clinical practice to differentiate between OA and NOA, but there are exceptions.

The line between OA and NOA begins to blur in long‐standing seminal tract obstruction[16,17]. Moreover, some cases of NOA with normal testicular volume and normal‐to‐borderline endocrine parameters may mimic OA[18]. A reproductive urologist may encounter challenging cases with unexpectedly low sperm yield (or even negative sperm retrieval) during surgical extraction attempt in suspected OA. Testicular pathology in such cases may demonstrate alterations typical for spermatogenic failure. There are several histological phenotypes behind NOA, the most common being hypospermatogenesis, maturation arrest, and Sertoli cell only (SCO) syndrome. In hypospermatogenesis, the least severe pattern, all stages of hypospermatogenesis are present, including elongated spermatids, though a decrease in germ cell number is observed. In maturation arrest spermatogenesis doesn't proceed beyond a certain stage. Finally, in SCO pattern there are no spermatogonia in seminiferous tubules.

The aim of this study was to describe, analyze, and classify possible challenges in differentiating between two types of azoospermia.

2 MATERIALS AND METHODS

We performed a retrospective review of database on surgical sperm retrieval attempts performed at andrology and urology department of V.I. Kulakov National Medical Research Center (Moscow, Russia). Overall number of azoospermic patients was 1417.

A subpopulation of 418 patients with normal testicular volume (a long axis measurement > 4.6 cm), normal testosterone (>12 nmol/l), and gonadotropin levels (FSH < 7.6 IU/l), who were preliminary diagnosed with OA, was selected for further analysis.

Sperm retrieval attempts in patients with suspected OA begun with microsurgical sperm aspiration (MESA) on the right side. If no sperm were found in epididymal fluid or if epididymal tubules could not be identified, simple TESE was attempted. If intraoperative embryological assessment of TESE sample provided unsatisfactory results, microTESE was attempted. In case of inadequate sperm yield, the same sequence was repeated on the left side.

All patients had testicular pathology data following sperm retrieval attempt. Some samples had histological features characteristic of spermatogenic failure (hypospermatogenesis, maturation arrest [MA], SCO), which prompted reclassification of azoospermia as non‐obstructive. Testis specimens were scored according to a scale proposed by Bergmann and Kliesch[19]. Rate of reclassification was assessed as a primary outcome. Reclassified cases were further analyzed to find a possible reason for incorrect differential diagnosis.

3 RESULTS

Among 418 patients with initially suspected OA, 243 (58.1%) had evidence of spermatogenic dysfunction on pathological examination of seminiferous tubules.

The largest group among reclassified cases was represented by 111 patients with clear etiology of long‐standing obstruction (>5 years) and no additional risk factors. There were cases caused by various congenital abnormalities (n = 49), bilateral epididymitis with or without history of sexually transmitted infections (n = 27), bilateral inguinal hernia surgery (n = 14), spermatocele excision (n = 8), vasectomy (n = 7), midline prostatic cysts (n = 4) and extensive surgery for anorectal malformation (n = 2). Congenital abnormalities were represented by bilateral absence of vas deferens (CBAVD) (n = 26), partial unilateral Wolffian duct abnormalities with agenesis of seminal vesicle (n = 16), complete unilateral Wolffian duct abnormalities with renal agenesis (n = 4), Zinner's syndrome (n = 2) and Young's syndrome with situs inversus (n = 1). Median duration of obstruction among these patients was 16.5 years (interquartile range [IQR]: 10–27). In case of an identified congenital abnormality, duration of obstruction was considered to be equal to the patient's age. In case of prostatic cysts, duration of obstruction was determined by an earliest imaging study which confirmed their presence. There were no other risk factors for spermatogenic failure among these patients beside long‐term obstruction of the seminal tract. Hypospermatogenesis was observed in most testicular parenchyma samples (n = 110), but there was one case of SCO histology. Median Bergmann–Kliesch score (BKS) was 5 (IQR: 4–6). There was a moderate negative correlation between BKS and duration of obstruction (r = −0.45; p < 0.005). Sperm retrieval rate was 100%, but in nine patients conversion to microTESE was necessary (Table 1). We provide description of several clinical cases to better illustrate our observations.

Documented history of acute bilateral epididymo‐orchitis was the sole cause of obstruction in 58 patients, and two patients had history of epididymo‐orchitis in a solitary testis. As opposed to simple epididymitis, epididymo‐orchitis was accompanied by fever, scrotal swelling, testicular pain, and tenderness on palpation. All 58 patients eventually underwent successful sperm retrieval, but in 20 patients epididymal sperm could not be obtained due to complete fibrosis of epididymis, and eight patients required microTESE due to negligible testicular sperm yield on random multifocal TESE. Median BKS was 4 (IQR: 2–6). Postinflammatory changes were evident on testicular pathology, which suggested that spermatogenic failure was secondary to descending inflammation of seminiferous tubules in acute epididymo‐orchitis. A description of clinical case is presented.

Twenty patients underwent prolonged treatment for male infertility (duration of treatment > 12 months) prior to referral or self‐initiated presentation to our center for second opinion. Upon proper evaluation, we were able to find seminal tract obstruction not amenable to medical therapy. Five patients had prostatic cysts, three patients had history of inguinal hernia surgery and 12 patients had congenital abnormalities which were missed on initial examination or probably ignored as clinically insignificant findings. Needless to say, occurrence of sperm in ejaculate would be a highly improbable outcome of medical therapy in these conditions. However, since obstruction was not diagnosed previously, these patients received empirical therapy for which, we believe, could have had negative impact on spermatogenesis. All 20 of them received some kind of empirical hormonal stimulation, most commonly clomiphene citrate and human chorionic gonadotropin, sometimes without proper baseline endocrine studies or follow‐up. For example, one patient received clomiphene 50 mg daily and tamoxifen 20 mg daily for at least 6 months in order to “induce spermatogenesis.” Some patients received testosterone therapy after the prescribing physician assured them about its alleged safety, despite androgens being contraindicated in men interested in reproduction. Eight patients in this group also received lengthy treatment for supposed chronic bacterial prostatitis causing distal seminal tract obstruction. Four patients among them received three 4‐week cycles of levofloxacin during the 12 months prior to presentation, all simultaneously with hormone therapy. It is difficult to describe and categorize the empirical treatment which those 20 patients received, it would suffice to say that medications were frequently prescribed in unusual combinations and dosages with unclear rationale. We deduced that spermatogenic failure in these patients was secondary to a lengthy treatment with medications potentially harmful to spermatogenesis (i.e., iatrogenic), as there were no other etiological factors which could lead to an impairment of spermatogenesis in what would be typical OA cases otherwise. Considering the presence of seminal tract obstruction we did not try to initiate proper hormonal stimulation and instead proceeded with surgical sperm retrieval. In 13 cases, MESA and simple multifocal TESE were sufficient to obtain epididymal and testicular sperm. However, seven other patients required conversion to microTESE. Even then, in four patients sperm retrieval attempt turned out to be unsuccessful. MicroTESE failures are probably caused by the fact that in both cases less than 2 months have passed since the cessation of aggressive empirical therapy, but we had to perform sperm extraction attempt without proper preparation because the female partner was already going for oocyte retrieval.

All previously described groups of patients had seminal tract obstruction as a primary cause of infertility and aggravating factors which caused spermatogenic failure. However, there were also 54 patients with true NOA caused by uniform maturation arrest at the level of primary spermatocytes, as pathology demonstrated (BKS = 0). Outcomes of sperm retrieval were poor. All patients required microTESE, which was successful only in three cases.

4 DISCUSSION

Our study revealed several clinical scenarios where differential diagnosis between OA and NOA becomes challenging. In most of them, seminal obstruction is a primary cause of infertility, but some factors cause secondary spermatogenic failure, which becomes evident on histological evaluation. Whether it is enough to reclassify long‐term or complicated OA as NOA is debatable. Probably “non‐obstructive azoospermia” is not even a proper term, since it may be interpreted to mean lack of obstruction, but there is no accepted terminology for such cases to our knowledge. However, we think that this reclassification of individual cases is reasonable, as it has a clear impact on prognosis and management. A parallel may be drawn with pathological upgrading in prostate cancer, when pathology reveals that the disease is more serious than originally thought.

We used a histological score proposed by Bergmann and Kliesch in routine clinical practice, as well as for this study. We believe that the percentage of seminiferous tubules containing elongated spermatids, upon which the BKS is based, has a better prognostic value for further sperm retrieval attempts when compared to Johnsen score. BKS covers all the spectrum of hypospermatogenesis, while specific unfavorable patterns like SCO syndrome and uniform MA are separated and given the value of 0. There is a clear correlation between the degree of spermatogenic failure and BKS, unlike Johnsen score which is nonlinear and may yield paradoxical results. For example, a patient with uniform MA would have a Johnsen score of 5 and extremely poor chances at sperm retrieval, while a patient with SCO syndrome would have a Johnsen score of 2 and a decent chance for a successful microTESE.

Sperm yields were lower than could be expected in typical OA. A significant number of patients required conversion to microTESE to find usable testicular sperm. Since not all fertility clinics are sufficiently equipped, future sperm retrieval attempts should be planned with this knowledge in mind.

Long‐term seminal tract obstruction may impair spermatogenesis due to increased pressure in seminiferous tubules or immunological mechanisms. Testis ischemia due to vascular damage couldn't be excluded as a separate factor in patients who underwent herniorrhaphy or vasectomy. It is well known that longer duration of obstruction has negative impact on outcomes of vasectomy reversal[20]. A study by Raleigh et al. demonstrated testicular fibrosis and impairment of later stages of spermatogenesis associated with longer obstructive intervals after vasectomy, likely due to induction of apoptosis[17]. Spermatogonia, primary spermatocytes, and Sertoli cells were seemingly unaffected, unlike in an earlier report by Shiraishi et al[21]. Considering this, patients should be counseled regarding sperm cryopreservation prior to vasectomy, as some of them may seek fertility in the future. We could not confirm these histological findings due to low number of vasectomized patients, as this contraception method is unpopular in Russia. Probably, the correlation between duration of obstruction and secondary spermatogenic failure is true for other conditions, including congenital abnormalities. Cito et al. reported a clinical case of a long‐term obstruction with complete SCO histology in a patient with Zinner syndrome[16]. Either this case was an extreme example of pattern observed in our study, or it was an idiopathic case of NOA coexisting with Zinner syndrome.

Azoospermia in patients with history of symptomatic epididymo‐orchitis does not seem to have a purely obstructive etiology. Sequelae of inflammation which ascended through rete testis to seminiferous tubules may directly impact spermatogenesis, as evidenced by postinflammatory changes with hypospermatogenesis on histology. Bacterial epididymitis spreads to the testicle in 40%–60% of cases[22,23]. Direct damage to germ cell epithelium by uropathogenic Escherichia coli infection in murine model was observed in a study by Klein et al., though it mostly resolved on Day 31 after induction of epididymo‐orchitis[24]. Immune‐mediated damage to seminiferous tubules in animal models was demonstrated by Bhushan et al[25]. Finally, obstructed testis is a closed environment, which can harbor asymptomatic chronic infection, being a separate risk factor for impaired spermatogenesis[26].

Management of azoospermia in centers not specializing in reproductive andrology may worsen reproductive outcomes, even if the patients are eventually referred to a specialized department. At the very least, an infertile couple may lose time trying to improve semen parameters through conservative means. We had 13 patients with congenital abnormalities causing seminal tract obstruction, which were not properly diagnosed during initial evaluation. They received aggressive treatment for more than 1 year expecting for the sperm to appear in ejaculate due to hormonal stimulation or resolution of supposed chronic prostatitis. It is known, however, that antibiotics, such as fluoroquinolones, may have a negative effect on testis tissue[27,28]. Medications used for hormonal stimulation of spermatogenesis are also not without risks. Paradoxical response to clomiphene treatment is well‐documented in nonazoospermic men, but it is hard to detect in azoospermia[29]. Human chorionic gonadotropin, another popular fertility drug, may also cause disruption of spermatogenesis, possibly through a negative feedback action on FSH[30,31]. Thus, clinicians should be aware of pitfalls of endocrine‐mediated therapy. Even though these patients were improperly managed from the start, their cases emphasize the rarely discussed challenges in differential diagnosis of azoospermia.

While previously discussed cases mostly have good sperm retrieval outcomes despite evidence of spermatogenic failure, patients with uniform maturation arrest had true NOA with adverse prognosis for reproduction. Some patients with sperm maturation arrest have low FSH levels and normal testicular volume, which makes this pattern mistaken for OA at initial presentation[18,32]. Sperm retrieval rates in patients with uniform maturation arrest and normal FSH tend to be even lower than in patients with other types of NOA[33]. However, maturation arrest seems to respond to recombinant FSH therapy, but an informed decision can not be made without testicular biopsy[34]. Clinicians should be aware that any case of presumed OA without a clear etiology and no corroborating imaging findings is suspicious. We have not used testicular sperm aspiration (TESA) procedure in our series. With a benefit of hindsight, we may argue that the efficacy of TESA would have been poor, judging by a significant rate of conversion to mircoTESE in all groups. As for the possible diagnostic value of needle biopsy, the only group which could benefit from it are the patients with uniform maturation arrest. Even then, this benefit is arguable, as the evidence for treatment of this condition (such as recombinant FSH therapy) is limited.

This study is based on a retrospective series, which is a limitation. We realize that its descriptive nature and patient selection bias are also limitations, but we believe that it may provide valuable information to clinicians and inform future prospective studies. As far as we know, the concept of azoospermia reclassification is new, and there were no attempts to classify spermatogenic failure in patients with presumed OA.

5 CONCLUSION

Early sperm retrieval and cryopreservation may be beneficial in patients with untreatable OA and indefinite reproductive life plans. Men with obstructive congenital abnormalities, history of pediatric inguinal‐scrotal surgery, and epididymo‐orchitis are at risk of spermatogenic failure. Finally, counseling of patients with normal testicular volume and endocrine parameters shouldn't be overly optimistic. They should be warned about a probability of conversion to microTESE and risks of negative sperm retrieval.

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